Link GDAL to consume a WFS

Question

I'm using a WFS that is openly available as a demo from the MapServer web site.

http://demo.mapserver.org/cgi-bin/wfs?SERVICE=WFS&VERSION=1.0.0&REQUEST=GetCapabilities

And now I want to make a client application that can consume this service in C++ (QT) using the GDAL libraries.

I have compiled GDAL with Xerces and curl as the docs say but apart from that they are not very clear about how to use it for a WFS, I'm sure the functionality is there because it says it supports it but I can't find any WFS specific documentation, so far I have just tried to open a connection and get this error:

GDALAllRegister();
const char *pszFilename = NULL;
pszFilename = "http://demo.mapserver.org/cgi-bin/wfs?";
m_dataset = (GDALDataset*) GDALOpen(pszFilename, GA_ReadOnly);

if( m_dataset == NULL )
{
    std::cout << "Dataset is empty" << std::endl;
    exit( 1 );
}

Error:

ERROR 4: `/vsimem/http_1/file.dat' not recognised as a supported file format.

Dataset is empty
ERROR 4: Failed to create temporary file:/tmp/file.dat

I have also tried instead of the URL, an XML document that contains the URL like the docs say this should work.

<OGRWFSDataSource>
    <URL>http://path/to/WFS/service[?OPTIONAL_PARAMETER1=VALUE[&amp;OPTIONNAL_PARAMETER2=VALUE]]</URL>
</OGRWFSDataSource> 

But this just says the file isn't a compatible type, any help would be appreciated here.

Answer 1

GDAL 1.x

GDAL versions < 2.0 have separate raster (gdal) and vector (ogr) libraries. Don't try to open the WFS vector data with GDAL, use OGR instead. GDAL supports raster data, OGR supports vector.

GDAL 2+

The raster and vector drivers are integrated into the gdal library and you use GDALOpenEx to open both raster and vector datasets. The ogr library/namespace is still available for backwards compatibility.

Here's a link to the WFS Driver documentation and the OGR API tutorial.